The Los Angeles Timesreports that an iconic road sign cautioning drivers near the San Diego border has quietly disappeared. The "immigrant crossing" signs have become obsolete, said Cathryne Bruce-Johnson, a spokeswoman for Caltrans. The transportation department stopped replacing the signs years ago because it constructed fences along medians to deter people from running across highways. The last sign, which stood on the side of the Interstate 5 Freeway near the San Ysidro border crossing, vanished in September and is assumed stolen.